Osteotomy is defined as a procedure for surgical division or sectioning of a bone. This procedure is typically utilized by orthopedic surgeons to correct for malalignment and malorientation, including uniapical and multiapical deformities of the bone, as well as the treatment for compartmental diseases. Bone deformities are the result of the continuous response and adaptation of the bone as a living tissue to several external and internal factors, such as physiological forces, alterations due to trauma, tumors, and other conditions. As a result, the shape of the bone can be severely deformed in three dimensions, comprising angulation in the frontal plane, angulation in the sagital plane, and rotation along the bone axis. Moreover, the deformity can be localized at a point, such as those deformities caused by a fracture or those deformities which spread along the bone as exemplified by those caused by a growth defect.
Displacement osteotomy is the surgical division of a bone and shifting of the divided ends to change the alignment of the bone or to alter weight-bearing stresses. The goal of displacement osteotomies is to create congruent matching surfaces to align, stabilize, and maximize contact between the corresponding bone sections. Osteotomies may include a number of different types of bone sectioning procedures that result in two corresponding sections of the bone which are then reoriented until a desired alignment between the bone sections is achieved. In order to improve stability, distribute the load evenly, eliminate abnormal stress, and aid healing, surgeons strive to maximize the match or contact area between two corresponding surfaces when surgically sectioning the bone. Representative types of bone cuts include simple transverse, obliqued cuneiform, stairstep, simple to complex wedges, barrel-vault, and dome shaped cuts. In practice, a surgeon may choose a specific cut configuration in order to achieve a particular reconfiguration of the bone being treated.
Although so-called “dome osteotomy” has been known for decades, the term “dome osteotomy” has been used to refer conventionally to semi-cylinder, i.e., half or part (partially) cylindrical, shaped surgical cuts. Specifically, amongst experts within the field, “cylindrical osteotomy” would be a more accurate descriptor for these types of so-called “dome” osteotomies, as it is well understood by all to be a cylindrically shaped cut. References to spherical osteotomies in the veterinary literature, to date in particular, have been poorly defined at best and misleading at worst. Although a dome descriptor suggests a truly spherical surface, dome osteotomies as referred to in both human and veterinary orthopedic literature have constituted cylindrical or crescent bone cuts. Although resulting shapes of so-called “dome” osteotomy are not domes, the following terms have been used in the scientific literature to refer to osteotomies wherein corresponding bone cuts are shaped like a semi-cylinder: dome, spherical, barrel-vault, focal dome (reversed dome), crescentic, and arcuate. These conventional forms of semi-cylindrically shaped osteotomies are better described as barrel-vault osteotomies, and will be described accordingly herein below. Further, the term “dome osteotomy” has been used in the literature and within the field of corrective osteotomy to describe barrel-vault osteotomy, however, the field of corrective osteotomy has lacked a method and device to accomplish, as described below with respect to the invention herein presented, what will be termed “true dome” or spherical osteotomy.
In barrel-vault osteotomy, a bone is sectioned by oscillating a saw blade around the central axis of the cylinder while cutting the bone. Barrel-vault osteotomy may be used to correct angulation about the central axis of the cylindrical cut and translation along the central axis of the cylindrical cut. The barrel-vault osteotomy provides and allows correction in two-dimensions, which sometimes results in undesirable secondary translation because of imparted limitation of two-dimensional repositioning of the bone portions. In this respect, barrel-vault osteotomy cannot be used to correct axial rotations of the bone without creating gaps and instability between bone segments thereby being a major limitation of so-called “barrel-vault” osteotomies. The success of barrel-vault osteotomies relies heavily on meticulous pre-operative planning, and while it may be used to correct radial deformities in the frontal and sagittal planes, one of its major disadvantages is the limited ability to correct axial rotational deformities. Accordingly, it would be desirable to provide a device capable of cutting a bone into corresponding sections that allows for correction in more than two-dimensions.
There are a variety of devices and methods available to accomplish these so-called “barrel-vault” osteotomies. One method includes drilling a series of holes in the bone along a planned arc. In one example, U.S. Pat. No. 6,190,390 discloses an apparatus and method for the surgical realignment of the knee through proximal tibial osteotomy. The apparatus has an arcuate profile configuration for establishing a series of parallel holes forming the desired semi-cylindrical contour of the barrel-vault cut. In addition to the general disadvantages of “barrel-vault” osteotomies mentioned above, such a method undesirably creates ridges between adjacent sets of drilled parallel holes making alignment more difficult and gaps between bone portions more probable.
According to another example, U.S. Pat. No. 4,955,888 discloses a biradial saw blade with an arcuate body, powered by oscillating motion that is used to create the barrel-vault osteotomy. Such saw blades are typically associated with a saw assembly which operates to displace the blade in a reciprocating motion by oscillating the blade around the drive axis of the saw assembly. The saw blade has a curved cutting edge at the end of the body shaped as a part of a cylinder for making barrel-vault shaped surgical cuts. While the cut resulting from the use of the biradial saw blade provides for a better match of the two surfaces of both bone portions, the heat and friction produced by the saw blade may be detrimental to the bone, specifically for allowing proper healing thereof. Also, other conventional “barrel-vault” saw blades may include a partially cylindrically shaped body having a cutting member on its leading edge.
Conventional blades are limited in providing semi-cylindrical cuts of the bone which limit the correction in the bone, particularly when correcting deformities that lie in two planes, such as the frontal and sagittal planes. Correction of deformities in two planes requires meticulous preoperative planning in order to determine the central axis about which the cut in the bone is to be made. This is especially crucial if the bone portions are to be properly positioned to correct the deformity. Cutting the bone about a different central axis will only allow, at best, partial correction in the two planes. Further, it is desirable to provide improvement for the correction of malalignment, malorientation, and compartmental disease, including other deformities of the bone by osteotomy procedures and tools. Accordingly, it would be desirable to provide an osteotomy tool for cutting bone that increases the adjustability of the bone portions, achieves optimal bone contact, and improves primary stability. It is also desirable to provide an osteotomy tool that is less dependent upon cutting the bone precisely about a determined central axis when attempting to achieve proper correction.
Another disadvantage associated with the use of so-called “barrel-vault” osteotomies is the limited ability to correct axial rotational deformities. Correction of other deformities may also be difficult to make, particularly when a correction of the deformity requires cutting the bone in a less accessible location. This makes it increasingly difficult for a surgeon to provide the corrective cut, as described above, where it is needed. Another disadvantage of barrel-vault osteotomies is the bone portions, after severance, may only be repositioned with respect to one another about two principal dimensions, one of the principal dimensions being an angular displacement or rotation about the central axis, and the other principal dimension being a lateral displacement or position along the central axis. The angular displacement or rotation allows the bone pieces to be rotated with respect to one another about the central axis to the desired correction. The lateral displacement or position allows the bone pieces to be positioned with respect to each other along the central axis to the desired correction. Also, the bone pieces may obtain the desired correction through a small combination of lateral displacements and angular displacements. Lateral displacement of the bone pieces is limited to the extent that the bone portions include sufficient surface contact for proper healing to occur. Angular displacement of the bone pieces provides for better bone-to-bone contact than lateral displacement, however, angular displacement is still limited if the bone portions are to be maintained with sufficient surface contact in order to provide for proper healing.
A dome saw blade for the execution of true spherical osteotomies has been made available under the trade designation DOMESAW by Matrix Orthopedics of Twin Falls, Id., however guidelines for spherical osteotomy preoperative analysis and planning using the osteotomy rule for spherical true dome osteotomies, the three-dimensional center of rotation and angulation (3D CORA), and 3D computer modeling have not been fully established. The traditional approach for osteomotic procedures as represented by the Paley rules are limited to techniques for performing two-dimensional cuts. Paley's rules, as articulated in Principles of Deformity Correction, D. Paley, Springer-Verlag, Berlin Pg 99-113 (2005), have not been updated to encompass the three-dimensional concept of a true spherical osteotomy (TSO). It follows that there is a need to provide a new method for preoperative analysis and planning of osteotomies directed to achieving true dome ostoetomies.
Current techniques of surgical planning for deformity correction typically include the taking of measurements of the bone from orthogonal X-ray projections and the computation of the angle to be corrected based on these measurements. The efficacy of the results achieved through the conventional process depends on the accuracy of the projections, the plane of the X-ray relative to the deformity to be corrected, the care taken in performing the measurements in the radiograph, and the accuracy of the calculations which are subsequently performed. Moreover, the figures of angulation and rotation obtained with this method can only be verified with the same procedure, performed through the use of different radiographs.
The use of two-dimensional images in the conventional process introduces a number of uncertainties into the planning process, including the difficulty of evaluating bone deformities in all directions and projections.
It would be desirable to provide a method for cutting a bone into corresponding sections resulting in a “true dome” or spherical osteotomy.
It would also be desirable to provide an osteotomy method for “true dome” or spherical osteotomies that would produce two substantially congruent (one concave and one convex) surfaces after the sectioning of the bone.
Furthermore, it is also desirable to provide a method which reduces, if not eliminates, the uncertainties associated with planning a surgical procedure from the limited perspective of two-dimensional images. It would be desirable if the new method would facilitate the three-dimensional evaluation of bone deformities from a number of perspectives and projections would permit the identification of optimal locations for performing a bone sectioning procedure, would establish an optimized angular orientation to which the sectioned bone may be realigned, and would furthermore simulate the result of the completed surgery. Optimally, the new pre-surgical analysis and planning method would perform all of these functions through a methodology which is interactive and capable of producing instant feedback to the clinician charged with the planning of the surgical procedure.